Structural and spectroscopic characterization of CO inhibition of [NiFe]‐hydrogenase from Citrobacter sp. S‐77

• Published in: Acta crystallographica. Section F, Structural biology communications Structural biology communications, 2022-02, Vol.78 (2), p.66-74
• Main Authors: Imanishi, Takahiro, Nishikawa, Koji, Taketa, Midori, Higuchi, Katsuhiro, Tai, Hulin, Hirota, Shun, Hojo, Hironobu, Kawakami, Toru, Hataguchi, Kiriko, Matsumoto, Kayoko, Ogata, Hideaki, Higuchi, Yoshiki
• Format: Article
• Language: English
• Subjects: [NiFe]‐hydrogenases; Bacterial Proteins - chemistry; Carbon monoxide; Carbon Monoxide - chemistry; Carbon Monoxide - metabolism; Carbon Monoxide - pharmacology; Catalytic Domain; Citrobacter; Citrobacter - enzymology; Citrobacter sp. S‐77; Crystal structure; Crystallography; Crystallography, X-Ray; Diamagnetism; Electron paramagnetic resonance; Electron spin resonance; Electron Spin Resonance Spectroscopy; Enzyme Inhibitors - chemistry; Enzyme Inhibitors - metabolism; Enzyme Inhibitors - pharmacology; Hydrogenase; Hydrogenase - antagonists & inhibitors; Hydrogenase - chemistry; Hydrogenase - metabolism; Infrared spectroscopy; inhibitors; Intermetallic compounds; Iron compounds; Models, Molecular; Nickel; Nickel compounds; Oxidation; Protein Conformation; Research Communications; spectroscopy; Spectroscopy, Fourier Transform Infrared; Spectrum analysis; Structural analysis; Vibration
• ISSN: 2053-230X; 2053-230X
• DOI: 10.1107/S2053230X22000188

Hydrogenases catalyze the reversible oxidation of H2. Carbon monoxide (CO) is known to be a competitive inhibitor of O2‐sensitive [NiFe]‐hydrogenases. Although the activities of some O2‐tolerant [NiFe]‐hydrogenases are unaffected by CO, the partially O2‐tolerant [NiFe]‐hydrogenase from Citrobacter sp. S‐77 (S77‐HYB) is inhibited by CO. In this work, the CO‐bound state of S77‐HYB was characterized by activity assays, spectroscopic techniques and X‐ray crystallography. Electron paramagnetic resonance spectroscopy showed a diamagnetic Ni2+ state, and Fourier‐transform infrared spectroscopy revealed the stretching vibration of the exogenous CO ligand. The crystal structure determined at 1.77 Å resolution revealed that CO binds weakly to the nickel ion in the Ni–Fe active site of S77‐HYB. These results suggest a positive correlation between O2 and CO tolerance in [NiFe]‐hydrogenases. The 1.77 Å resolution crystal structure of the CO‐bound state of [NiFe]‐hydrogenase from Citrobacter sp. S‐77 revealed that the exogenous CO ligand binds to the nickel ion in a bent conformation. The CO‐bound state was identified as an EPR‐silent Ni‐SCO state by EPR and FT‐IR spectroscopy.